Generally, a rod lens array unit including a rod lens array in which a plurality of distributed index type rod lenses (hereinafter referred to as “rod lenses”) are arranged along a predetermined direction is used as, for example, an LED print head used as an exposure device such as an LED (light Emitting Diode) printer, etc., and an image sensor head used as a reader such as an image scanner, etc. In a rod lens array unit, it is desired to reduce the variation in focal length of the rod lenses along the arrangement direction of the plurality of rod lenses included in the rod lens array. Further, it is desired that an excellent optical performance of the rod lens array unit is maintained by forming each of the end faces of the plurality of rod lenses as a mirror finished surface. Therefore, a method is proposed, in which, at the time of producing the rod lens array unit, a rod lens array is arranged between a pair of side plates that sandwiches and holds the rod lens array, and the edge part of the rod lens array and the side plates are cut to align the lengths of the plurality of rod lenses and finish the end faces of the rod lens array into mirror finished surfaces (for example, see Patent Document 1).
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 2005-181949
However, at the time of producing the rod lens array unit, for example, chips, etc., may remain at the edge parts of the side plates when cutting the edge parts of the rod lens array together with the side plates in a state in which the rod lens array is arranged between a pair of side plates. When the chips, etc., adhere to the end faces of the rod lens array, there was a problem that a stable optical performance could not be achieved.
The present invention aims to provide a rod lens array unit capable of achieving a stable optical performance, a production method of the rod lens array unit, an LED print head including the rod lens array unit, an image sensor head including the rod lens array unit, an image forming apparatus including the LED print head, and an image reader including the image sensor head.